Sir Alan Sugar, the star of BBC2's surprise reality hit The Apprentice, has savaged the corporation, claiming if it were run like a business "80% of [its staff] would be out of a job".

The no-nonsense founder of Amstrad, who has been enjoying renewed fame on the back of the show, criticised the programme's makers for their "lack of brain power".

"If it was ever run like a business, 80% of them would be out of a job," he told a fundraiser at the Savoy Hotel in London.

Sir Alan said he raised the thorny issue of how to keep the identity of the show's winner secret when filming began last year, and was reassured that the "creative internal people" would find a solution.

But just before the dramatic climax of The Apprentice was filmed last October, production staff realised the problem had not been solved and "panic set in".

According to today's Jewish Chronicle, he added: "I'm afraid to say that, within the organisation, there's not a lot of brain power."

The solution was to shoot two endings. The two finalists, Saira Khan and the eventual winner, Tim Campbell, were employed by Amstrad on a temporary basis for the six months before the programme was broadcast.

"The nasty thing was when one poor sod thought they had won, and then I said: 'Actually, it's only a joke, we're going to do that again'," he said.

Sir Alan's remarks come as it emerged that Khan, 35, has spurned the opportunity to work with the self-made millionaire in favour a career in the media.

She has been given a break as a guest reporter on BBC Radio 5 Live - but she is so confident of her longevity as a reality TV graduate that she has hired an agent to maximise her potential.

Khan told the Guardian last month: "I think Sir Alan thought I was a threat. He was scared to hire me."

And in a cryptic remark, made to the Daily Mail yesterday, she said: "Sir Alan knows the reasons why I didn't want to take the job - you'll just have to ask him.

"I have an agent who is currently holding discussions about a number of different opportunities. You'll have to watch this space."

At the fundraising lunch, Sir Alan also criticised the candidates selected to compete on The Apprentice for an Amstrad job with a six-figure salary. Some were "a bit brain dead, to say the least", he said.

The final episode of The Apprentice, screened in early May, attracted a very healthy audience of 4 million people - a 16 per cent share - to BBC2. This is about one million more viewers than the average audience for the show over its 12-week run.

Last month Roly Keating, the BBC2 controller, said the show, made by Talkback Thames, would be recommissioned for a second series.

The programme is an adaptation of an NBC show fronted in the US by entrepreneur Donald Trump. Talkback Thames snapped up the format and sold it to the BBC after the broadcaster initially turned it down.

Daisy Goodwin, the show's executive producer and the Talkback editorial director, said The Apprentice was "a triumph for entertainment programming" and proved viewers wanted more than just wall-to-wall celebrities.

At the fundraising event, Sir Alan also called US tycoon Malcolm Glazer a "nutter" for the terms under which he had bought Manchester United. Sir Alan said he could not understand why Mr Glazer had bought the club. "Maybe it's a trophy," he said.